Asymmetrical Laminate Panel and Method of Manufacture

ABSTRACT

The present disclosure relates generally to plaster wall panels, for example, suitable for covering interior wall frames. The present disclosure relates more particularly to a plaster wall panel including a first plaster layer, a second plaster layer, and a damping layer disposed between the first and second plaster layers. The first plaster layer has a first thickness and is composed of a first plaster material that has a first material property. The second plaster layer has a second thickness and is composed of a second plaster material that has a second material property. The first thickness is smaller than the second thickness, and the first and second material properties are different.

BACKGROUND OF THE DISCLOSURE 1. Field of the Disclosure

The present disclosure relates generally to plaster wall panels andmethods for making plaster wall panels. The present disclosure relatesmore particularly to plaster wall panels having an asymmetrical laminateconstruction including a damping layer.

2. Technical Background

Plaster panels, often called “sheet rock” or “drywall”, are typicallyused to construct walls within homes, businesses, or other buildings.Plaster panels are very often made of gypsum, but other materials,including lime and cement, are also used. A typical method for making aplaster wall panel involves dispensing and spreading a plaster material(e.g., a slurry of gypsum in water) onto a paper sheet or fiberglass maton a platform, and covering the plaster material with another papersheet or fiberglass mat. This sandwiched structure is fed throughrollers to provide a structure of a desired thickness, then allowed tocure to form a hardened plaster material disposed between the two sheetsof paper or fiberglass. The plaster wall panel may be cut into sectionshaving predetermined lengths and widths that conform to acceptedconstruction standards.

Soundproofing is becoming an ever-increasing concern for theconstruction industry, for example, for use in residences, hotels,schools, and hospitals. Soundproofing is also desirable in theconstruction of theaters and music studios, to insulate noise made inthose areas from surrounding rooms. Model building codes and designguidelines often specify minimum Sound Transmission Class values forwall structures within buildings. While a number of constructiontechniques have been used to address the problem of soundproofing, oneespecially desirable technique uses sound-damping plaster wall panelsthat can be used in place of conventional drywall boards in variousresidential or commercial structures.

A sound-damping panel typically includes a damping sheet havingviscoelastic properties disposed between two layers of hardened plastermaterial. Some methods for making a sound-damping panel include a“two-step” process of forming a plaster wall panel as described above,slicing the plaster panel in half through its thickness, then bondingthe exposed plaster surfaces together with an adhesive that cures into aviscoelastic polymer. While this process can leverage existing plasterpanel manufacturing processes, it is disadvantageous in at least twoways. First, it involves cutting the plaster wall panel, which is notonly time consuming and messy, but can also structurally weaken theplaster material. Second, it involves a separate process of laminatingthe two plaster panel sections together with the viscoelastic material,which can create product defects such as misalignment of the twosections and delamination, if the viscoelastic material does not havesufficient adhesion strength.

Accordingly, what are needed are laminated sound-damping plaster wallpanels that have excellent sound-damping characteristics but can bemanufactured more easily, and a method to make such plaster wall panels.

SUMMARY OF THE DISCLOSURE

In one aspect, the present disclosure provides a plaster wall panelcomprising:

a first plaster layer having a first thickness and being composed of afirst plaster material having a first material property;

a second plaster layer having a second thickness and being composed of asecond plaster material having a second material property, wherein thefirst thickness is smaller than the second thickness and wherein thefirst and second material properties are different; and

a damping layer disposed between the first plaster layer and the secondplaster layer.

In another aspect, the disclosure provides a method of forming a plasterwall panel according to the disclosure, the method comprising:

providing a first wet plaster precursor;

providing a second wet plaster precursor;

positioning a damping layer or a precursor therefor between the firstwet plaster precursor and the second wet plaster precursor; and

drying the first and second wet plaster precursors such that the firstplaster precursor hardens into the first plaster layer having the firstthickness and the second plaster precursor hardens into the secondplaster layer having the second thickness.

Additional aspects of the disclosure will be evident from the disclosureherein.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the methods and devices of the disclosure, and areincorporated in and constitute a part of this specification. Thedrawings are not necessarily to scale, and sizes of various elements maybe distorted for clarity. The drawings illustrate one or moreembodiment(s) of the disclosure, and together with the description serveto explain the principles and operation of the disclosure.

FIG. 1 is a schematic perspective view of a plaster wall panel accordingto an embodiment of the disclosure;

FIG. 2 is a schematic cross-sectional view of a portion of the plasterwall panel of FIG. 1;

FIG. 3 is a set of transmission loss curves for panels having a range ofbottom layer thicknesses, the order of traces, from top to bottom, at afrequency of 3×10³ is 7.93 mm, 6.35 mm, 4.76 mm, 3.17 mm, and Standard;

FIG. 4 is a schematic cross-sectional view of a portion of a plasterwall panel according to another embodiment of the disclosure;

FIG. 5 is a schematic cross-sectional view of a portion of a plasterwall panel according to another embodiment of the disclosure;

FIG. 6 is a schematic side view of an apparatus used in a method offorming a wall panel according to an embodiment of the disclosure;

FIG. 7 is a graph showing the damping loss factor for wall panels with arange of layer thicknesses using materials of various density andelastic moduli;

FIG. 8 is a graph showing a relationship between the ratio of thethickness of the first and second layers and the ratio of the elasticmodulus of the first and second materials

FIG. 9 is a graph showing the average damping loss factor of threesamples of laminate structures; and

FIG. 10 is a graph showing the damping loss factor of three samples oflaminate structures under different vibration modes.

DETAILED DESCRIPTION

As described above, the present inventors have noted that conventionallaminate wall panels are difficult to manufacture. The present inventorshave determined that a modification of the material properties of thethinner layer of an asymmetrical wall panel can reduce the soundtransmission through the panel.

Accordingly, one aspect of the disclosure is a plaster wall panelincluding a first plaster layer having a first thickness and beingcomposed of a first plaster material having a first material property,and a second plaster layer having a second thickness and being composedof a second plaster material having a second material property. Thefirst thickness is smaller than the second thickness, and the first andsecond material properties are different. The plaster wall panel alsoincludes a damping layer disposed between the first plaster layer andthe second plaster layer.

Such a plaster wall panel is shown in perspective view in FIG. 1.Plaster wall panel 100 includes a substantially planar laminatestructure 110 with layers stacked to form an overall thickness 112.Plaster wall panel 100 also has a length 114 and a breadth 116 andincludes first and second surfaces 120, 122 that extend between opposinglong edges 124 and short edges 126. The layers of laminate structure 110are schematically depicted in FIG. 2. Plaster wall panel 100 includes afirst plaster layer 130 having a first thickness 132 and a secondplaster layer 140 having a second thickness 142. First plaster layer 130is formed of a first plaster material and second plaster layer 140 isformed of a second plaster material, where the first and second plastermaterials have at least one material property that is different. Adamping layer 150 is disposed between the first plaster layer 130 andsecond plaster layer 140.

As the person of ordinary skill in the art will appreciate, the plasterlayers described herein may be made using a variety of differentinorganic base materials. For example, in certain embodiments of theplaster wall panels and methods as otherwise described herein, at leastone of the first plaster material and second plaster material comprisesa base material that is a gypsum material. In other words, one or bothof the first and second plaster materials comprises a base material thatis a gypsum material. In other embodiments of the plaster wall panelsand methods as otherwise described herein, at least one of the firstplaster material and second plaster material comprises a base materialthat is, for example, lime or cement. As described herein, the first andsecond plaster materials are hardened plaster materials, for examplethat have set from a slurry. In certain embodiments, the first andsecond plaster materials include respective base materials. Further, aswill be appreciated by the person of ordinary skill in the art, thefirst and second plaster materials may include one or more fillers oradditives in the base plaster material(s), e.g., fiberglass, aplasticizer material, a foaming agent, and/or ethylenediaminetetraaceticacid (EDTA).

In certain embodiments, the damping layer provides an acoustic layer,i.e., a layer that can provide the overall structure with reduced soundtransmission (i.e., as compared to an otherwise identical plaster boardlacking the acoustic layer). In particular, the damping layer canprovide an increased damping loss to the overall structure (i.e., ascompared to an otherwise identical plaster wall panel lacking thedamping layer). While the detailed description of the presentspecification focuses primarily on viscoelastic polymer layers as anexample, the person of ordinary skill in the art will appreciate thatlayers of other material can be present in the plaster wall panel. Forexample, a different type of acoustic layer can be used (i.e., insteadof or in addition to a viscoelastic polymer), e.g., a layer thatdecouples vibrations in the first plaster layer from the second plasterlayer, or vice versa.

In certain embodiments, the damping layer has a damping loss factorgreater than 1%, e.g., greater than 2%, or greater than 3%, or greaterthan 5%, or greater than 10%, for example, in the range of 1%-50%, or2%-50%, or 3%-50%, or 5%-50%, or 10%-50%, or 1%-40%, or 2%-40%, or3%-40%, or 5%-40%, or 10%-40%, or 1%-30%, or 2%-30%, or 3%-30%, or5%-30%, or 10%-30%. This can be compared with the much lower value,e.g., lower than 1% for typical plaster materials such as gypsum. Asreferred to herein, and as would be appreciated by the person ofordinary skill in the art, a “damping loss factor” is a dimensionlessmetric of how efficient a material is at dissipating mechanicalvibrations (e.g., sound waves) as heat. In a laminated gypsum board, asin other laminated structures, the working mechanism for noise andvibration control is known as constrained layer damping (CLD). Energydissipation in laminated gypsum boards is achieved by shearing theviscoelastic polymer between two layers of gypsum. The energydissipation provided by the interlayer is quantified by the loss factor(q), a dimensionless quantity that can be measured directly or predictedfrom the modal damping of a dynamic system based on the RKU algorithm.Several standards are available for measuring the damping of a laminatedstructure (e.g., SAE J1737 or ISP 16940-2009); however, as used herein,ASTM E75-05 is used to measure the damping loss factor. Damping lossfactor is further described in Crane, R. and Gillespie, J., “A RobustTesting Method for Determination of the Damping Loss Factor ofComposites,” Journal of Composites, Technology and Research, Vol. 14,No. 2, 1992, pp. 70-79; Kerwin et al., “Damping of Flexural Vibrationsby means of Constrained Viscoelastic Laminate,” Journal of AcousticSociety of America, 1959,pp. 952-962; and Ross, D. et al., “Damping ofFlexural Vibrations by Means of Viscoelastic laminate”, in StructuralDamping, ASME, New York, 1959.

In conventional laminate panels, where the damping layer is disposedbetween sections of a panel that has been cut into upper and lowersections, the transmission loss is greatest if the two sections have thesame thickness. Any difference in the thickness between the two opposingsections reduces the transmission loss of the panel. The impact of thedifference in thickness between the layers can be seen in FIG. 3, whichshows transmission loss over a range of frequencies for several panelsthat have an overall thickness of 15.8 mm. Each of the laminate panelsrepresented in FIG. 3 use the same material in both layers. In FIG. 3,the panel that shows the least transmission loss is a standard panelwith only a single layer of plaster material and without any dampinglayer. In contrast, the panel that demonstrates the greatesttransmission loss is the panel that has the damping layer disposed inthe middle of the panel, such that the both layers are of equalthickness. The other lines in FIG. 3 represent other configurationswhere the overall thickness remains at 15.8 mm, but the thickness of oneof the layers is reduced. Specifically, the data shows that a greaterdifference between the thickness of the layers results in lowertransmission loss.

The present inventors have determined that the reduction in transmissionloss that results from differences in thickness between the two layersof the panel is a consequence of the differences in the flexuralrigidity (or bending stiffness) of the two layers. As used herein, ASTMC473-17 is used to measure flexural rigidity. The flexural rigidity ofmost structures decreases as the structure is made thinner, particularlyif the same material is used. For example, a thick plate of steel has amuch higher flexural rigidity than a thin plate of steel, which may bevery flexible. Accordingly, in a conventional laminate panel, if the twolayers of the panel are constructed at different thicknesses so that thepanel is asymmetrical, the thinner layer has a smaller flexural rigiditythan the thicker layer. This results in a reduced transmission loss ofthe panel, as a whole.

The present inventors have also determined that a reduction intransmission loss caused by the geometric asymmetry of the wall panelcan be avoided by increasing the flexural rigidity of the thinner layer.In particular, in embodiments of the disclosure, at least one of thematerial properties of the first and second layers is different, so thatthe flexural rigidity of the thinner first layer can more closely matchthat of the thicker second layer. Specifically, in certain embodiments,the thinner first layer has material properties such that it has ahigher flexural rigidity compared to a layer of the same thickness thatis made with the same material properties of the second layer.

In certain embodiments as otherwise described herein, the firstthickness is in a range from 3% to 75% of the second thickness, e.g.,from 5% to 50%, e.g., from 5% to 10%, or from 10% to 20%, or from 20% to30%, or from 30% to 40% or from 40% to 50%, e.g., 45% to 50%. Thethickness of the each of the layers, as described herein, is measured inthe direction that is perpendicular to the planar surface of the wallpanel. The difference in thickness can allow the laminate wall panelstructure to be fabricated more easily than if the first and secondlayers were of equal thickness.

In certain embodiments as otherwise described herein, the elasticmodulus of the first plaster material is greater than the elasticmodulus of the second plaster material. In certain embodiments, theelastic modulus of the first plaster material is in a range from 150% to1000% of the elastic modulus of the second plaster material, e.g., from150% to 200%, or from 200% to 300%, or from 300% to 400%, or from 400%to 500%, or from 500% to 600%, or from 600% to 700%, or from 700% to800%, or from 800% to 900% or from 900% to 1000%. The elastic modulus ofthe material within a plaster layer has a significant impact on theflexural stiffness of the layer. In particular, a plaster layer composedof a material structure having a higher elastic modulus can regain someof the flexural rigidity that might be “lost” as a result of reducingthe thickness of the layer. Thus, a layer with a lower thickness but ahigher elastic modulus can have a similar flexural rigidity as a layerwith a greater thickness but a lower elastic modulus.

In certain embodiments as otherwise described herein, the density of thefirst plaster material is greater than the density of the second plastermaterial. In certain embodiments, the density of the first plastermaterial is in a range from 110% to 400% of the density of the secondplaster material, e.g., from 120% to 300%, e.g., from 120% to 150%, orfrom 150% to 200%, or from 200% to 250%, or from 250% to 300%. Thedensity of a material can also impact the flexural rigidity of astructure made of that material. Likewise, variances in the density of aplaster material can vary the elastic modulus of a material, which willimpact structures composed of the material, as explained above. Indeed,in some cases, the density of a plaster material can have a directcorrelation with the elastic modulus. As will be appreciated by those ofskill in the art, the density of the first and second plaster materialscan be differentiated using different concentrations of foaming agents,fillers, or other additives. Likewise, one of the layers can include afoaming agent, filler or additive that is absent in the other todifferentiate the density of the first and second plaster materials.

In certain embodiments as otherwise described herein, the first plastermaterial has a different composition than the second plaster material.For example, the first plaster material and second plaster material mayinclude different fillers, binders, plasticizers or other agents thatimpact the flexural rigidity of the respective layer. These differencesin the material composition can result in different densities, asdescribed above, or they can result in materials with similar or thesame density but that impact flexural rigidity in different ways.Accordingly, the composition of the first plaster material can beformulated to have a stronger influence on increasing the flexuralrigidity of the first layer than the second plaster material has on thesecond layer. Thus, the difference in flexural rigidity between the twoboards that would otherwise result from the difference in thicknessescan be reduced. In certain embodiments, the base material of the firstplaster material and the second plaster material can be different.

For example, in certain embodiments as otherwise described herein, thefirst plaster material comprises a base material that is a gypsummaterial and the second plaster material comprises a base material thatis lime or a cement. Likewise, in other embodiments, the first plastermaterial comprises a base material that is a lime or a cement and thesecond plaster material comprises a base material that is a gypsummaterial.

In certain embodiments as otherwise described herein, the first plastermaterial and second plaster material include a different concentrationof additives that impact the flexural rigidity of the plaster layers,e.g., foaming agents, sodium trimetaphosphate, or polymer additives suchas hydroxyethyl methyl cellulose, polyvinyl acetate and dextrin. Forexample, in some embodiments, the second layer includes a largerconcentration of foaming agent. The higher concentration of foamingagent in the second layer results in a lower density of the secondlayer, which reduces its flexural rigidity. In some embodiments, thefirst layer includes sodium trimetaphosphate, which may increase theflexural rigidity of the first layer. Further, in some embodiments, thefirst layer includes polymer additives that add strength of the firstlayer so as to increase its structural rigidity.

In certain embodiments, the first layer (or both layers) includesreinforcing fibers to strengthen the respective layer. Suitable fibersinclude glass fibers or any of a range of organic fibers. In accordancewith embodiments of the disclosure, these fibers can be used in therespective layers in ways that provide different material propertieswhich impact the flexural rigidity of the layers themselves. Forexample, in certain embodiments as otherwise described herein, the firstplaster layer includes a higher concentration of reinforcing fibers thanthe second plaster layer. In some embodiments, the first layer mayinclude reinforcing fibers while the second layer is free of anyreinforcing fibers.

In certain embodiments as otherwise described herein, the first materialand second materials are anisotropic, and the orientation of the firstmaterial in the first plaster layer is different than the orientation ofthe second material in the second plaster layer. For example, in certainembodiments, reinforcing fibers are included in the layers, as describedabove, and the reinforcing fibers are arranged in a particularorientation. Further, in some embodiments, the orientation of the fibersin the first layer is different from the orientation of the fibers inthe second layer. In other embodiments the material of the layersincludes grains or other microstructures that form an anisotropicstructure, and within the first and second plaster layers theorientation of these grains or microstructures is different.

As mentioned above, in certain embodiments as otherwise describedherein, the damping layer is formed of a damping polymer. As the personof ordinary skill in the art will appreciate, a variety of materials canbe used as the damping polymer, for example, a so-called “viscoelasticpolymer.” In various particular embodiments, the damping polymer is inthe form of a glue, a resin, or an epoxy, for example.

In various embodiments of the plaster wall panels, the viscoelasticpolymer is polyvinyl butyral, a silicone, or an acrylic. Theviscoelastic polymer can be a thermally-cured material, e.g., a curedadhesive such as those available under the tradenames GreenGlue. Variousviscoelastic glues made by Weber may also be suitable for use. Dampingpolymer compositions are also described in U.S. Pat. No. 8,028,800 andU.S. Pat. No. 9,157,241, each of which is hereby incorporated herein byreference in its entirety.

In certain embodiments, the damping polymer exhibits large stress/straindelay or phase difference under loading. These materials can becharacterized by Dynamic-Mechanical Analysis (DMA), a technique commonlyused to measure the mechanical and damping properties of polymermaterials. The shear modulus (also known as the modulus of rigidity) isdefined as the ratio of shear stress to shear strain; in certainparticular embodiments as otherwise described herein, the dampingpolymer has a shear modulus in the range of 10 kPa to 100 MPa, e.g., 10kPa-50 MPa, or 10 kPa-10 MPa, or 10 kPa-1 MPa, or 50 kPa to 100 MPa, or50 kPa-50 MPa, or 50 kPa-10 MPa, or 50 kPa-1 MPa, or 100 kPa to 100 MPa,or 100 kPa-50 MPa, or 100 kPa-10 MPa, or 100 kPa-1 MPa. This can becompared to the elastic modulus of plaster materials (e.g., ˜2 GPa forgypsum).

In certain embodiments of the plaster wall panel and methods asdescribed herein, the damping layer is substantially less rigid than thehardened plaster material. For example, in certain embodiments, thedamping layer is at least 20% less, or even at least about 40% lessrigid or stiff than either of the first plaster layer or the secondplaster layer. In some embodiments, the plaster wall panel issubstantially less rigid (e.g., at least 20% less rigid or at least 40%less rigid) than an otherwise identical plaster wall panel lacking thedamping layer.

In certain embodiments as otherwise described herein, the dampingpolymer includes or is filled with a fire resistant material (e.g., zincborate) and/or a mold resistant material. Similarly, in someembodiments, one or both of first and second plaster layers include afire resistant material and/or mold resistant materials. Further, insome embodiments, each of the first plaster layer, second plaster layer,and damping layer include such fire resistant material and/or moldresistant material.

The plaster wall panel according to the present disclosure can have awide variety of different shapes and geometries. As set forth above, insome embodiments, the plaster wall panel is substantially planar. Thephrase substantially planar, as used herein, refers to a panel that issignificantly larger in length and breadth than in thickness. Forexample, the panel has a length and a width that is at least five timeslarger than the thickness of the panel, and in some cases the differencein these dimensions is significantly larger. It should be understoodthat a planar panel is planar in the sense of its general dimensions.Such a panel may have rough or textured surfaces and still be planar. Inother embodiments, the panel may include a significant curve and not beplanar.

The plaster wall panels of the present disclosure may be made in avariety of thicknesses. The person of ordinary skill in the art willselect a desirable thickness for a particular end use. In certainembodiments of the plaster wall panels, the total thickness of thelaminate structure is at least 5 mm and no more than about 50 mm. Forexample, in some embodiments, the thickness of the panel is in a rangefrom 5 mm to 25 mm, or in a range from 6 mm to 20 mm. For example, insome embodiments, the thickness of the panel is about 6 mm, such as a ¼inch panel. In other embodiments, the thickness of the panel is about 10mm or about 13 mm, such as ⅜ inch or ½ panels. Still, in otherembodiments the thickness of the panel is about 16 mm, such as ⅝ inchpanels. Further still, in some particular embodiments the boards have athickness of about 25 mm or 50 mm.

In certain embodiments as otherwise described herein, a length of theplaster wall panel is in a range from 6 feet to 24 feet, e.g., in arange from 8 feet to 20 feet, e.g., about 8 feet, about 9 feet, about 10feet, about 12 feet, about 14 feet, about 16 feet, or about 20 feet. Incertain embodiments as otherwise described herein, a width of theplaster wall panel is in a range from 24 inches to 96 inches, e.g., from36 inches to 72 inches, e.g., about 48 inches or about 54 inches. Otherlengths and widths are also possible.

In certain embodiments as otherwise described herein, the damping layerextends continuously across an entire length of the plaster wall panel.For example, in some embodiments, the material forming the damping layerextends from an edge of the wall panel at one end continuously to anopposing end at the opposite end of the panel.

In certain embodiments as otherwise described herein, the damping layerextends continuously across a portion of the width of the plaster wallpanel from within 5 inches of a first long edge of the plaster wallpanel to within 5 inches of a second long edge of the plaster wallpanel. For example, in some embodiments, the material forming thedamping layer extends across the majority of the width of the panel towithin a certain short distance to the side edges, or long edges, of thepanel. In some embodiments, the damping layer stops short of the edges,for example to accommodate a tapered edge of the panel. In otherembodiments, the damping layer extends continuously across an entirewidth of the plaster wall panel.

In certain embodiments as otherwise described herein, the damping layerextends continuously across a portion of the length of the plaster wallpanel from within 5 inches of a first short edge of the plaster wallpanel to within 5 inches of a second short edge of the plaster wallpanel. For example, in some embodiments, the material forming thedamping layer extends across the majority of the length of the panel towithin a certain short distance to the end edges, or short edges, of thepanel. In some embodiments, the damping layer stops short of the shortedges. In other embodiments, the damping layer extends continuouslyacross an entire width of the plaster wall panel.

Still, in other embodiments, the material of the damping layer issegmented into sections between the first and second plaster layers. Forexample, in some embodiments, the damping layer is formed by a pluralityof segmented sections of a damping material, such as a damping polymer,that are separated from one another. In some embodiments, the segmentedsections are provided in a regular pattern, for example, as strips ofthe damping polymer, or in a checkerboard pattern. Such strips ofdamping polymer may extend along the length of the plaster wall panel,or across the width of the plaster wall panel. Other patterns are alsopossible, as will be appreciated by those of ordinary skill in the art.

In certain embodiments as otherwise described herein, the damping layerhas a first surface that contacts the first plaster layer and a secondsurface that contacts the second plaster layer. In other words, in someembodiments, no layers other than the damping layer are provided betweenthe first plaster layer and the second plaster layer. In particular, insuch embodiments, the damping layer is in contact with the first plastermaterial of the first plaster layer and in contact with the secondplaster layer of the second plaster material, without any additionallayers or materials between the damping layer and the respective plastermaterial of the first or second layers.

In certain embodiments as otherwise described herein, the damping layerincludes a damping polymer that extends from the first surface to thesecond surface and contacts the first plaster layer and the secondplaster layer. In other words, in certain embodiments the damping layerincludes a damping polymer without any additional layers, and thedamping polymer extends from first plaster layer to the second plasterlayer without any additional layers between the first and second plasterlayers. In particular, in these embodiments, the damping polymercontacts both the first plaster material of the first plaster layer andthe second plaster material of the second plaster layer without anylayers other than that of the damping polymer between the first andsecond plaster layers. For example, plaster wall panel 100, shown inFIG. 1, includes such a damping layer. Specifically, damping layer 150includes a damping polymer 152 that extends from first plaster layer 130to second plaster layer 140.

In other embodiments, the damping layer includes a damping polymerdisposed on a carrier sheet. Such a damping layer can be made byapplying a precursor of the damping polymer on a carrier sheet,disposing the precursor-coated carrier sheet between plaster layers, andallowing the precursor to cure while between the first and secondplaster layers (e.g., as the first and second plaster materials dry).Alternatively a pre-formed carrier sheet with the damping polymerdisposed thereon can be disposed between the first and second plasterlayers, which are then allowed to dry.

The carrier sheet can be formed from a variety of materials, e.g., sheetmaterials that are capable of carrying a damping polymer. For example,in certain embodiments of the plaster wall panel and methods asdescribed herein, the carrier sheet comprises (or is) a paper sheet. Inother embodiments of the plaster wall panel and methods as describedherein, the carrier sheet comprises (or is) a fiberglass mat or afiberglass fabric. In other embodiments of the plaster wall panel andmethods as described herein, the carrier sheet comprises (or is) a wovenor non-woven fabric, such as a felt. In other embodiments of the plasterwall panel and methods as described herein, the carrier sheet comprises(or is) a sheet of foamed polymer, e.g., the foamed polymer sheet soldby BASF under the trade name BASOTECT. In other embodiments of theplaster wall panel and methods as described herein, the carrier sheetcomprises (or is) a polymer sheet, e.g., a thin polymer sheet of thetype typically used as a plastic release liner for an adhesive, whichcan be, for example in the range of 0.001-0.002″ thick. In otherembodiments, the carrier sheet can be an adhesive sheet, e.g., withadhesive such as a pressure-sensitive adhesive presented at one or bothsurfaces thereof. Such pressure-sensitive adhesive sheets can be formedfrom a core sheet (made, e.g., from PVC or

PET) with adhesive (e.g., a silicone pressure-sensitive adhesive or apolyacrylate adhesive) disposed on both sides thereof. Any releaseliners can be removed before use

The damping polymer can be disposed on the carrier sheet in variety ofmanners. For example, in certain embodiments of the plaster wall paneland methods as described herein, the damping polymer is impregnated onthe carrier sheet (e.g., when the carrier sheet has some level ofporosity). In certain embodiments, the damping polymer is formed as alayer on one or both sides of the carrier sheet. The damping polymercan, for example, be impregnated into the pores of the carrier sheet andform layers on either side of the carrier sheet.

In certain embodiments as otherwise described herein, where the dampinglayer includes a damping polymer on a carrier sheet, the damping polymercontacts one of the first plaster layer or second plaster layer, and thecarrier sheet contacts the other of the first plaster layer or secondplaster layer. In particular, in such embodiments, the carrier sheet anddamping polymer components of the damping layer directly contact theplaster material of the respective plaster layers. A plaster wall panelincluding such a damping layer is shown in FIG. 4. Plaster wall panel400 includes a first plaster layer 430 and a second plaster layer 440with a damping layer 450 disposed therebetween. Damping layer 450includes a sublayer of damping polymer 452 disposed on a damping sheet454. The damping sheet 454 is disposed on and contacts first layer 430,while damping polymer 454 contacts second plaster layer 440.

In other embodiments, additional layers are included between the firstand second plaster layers, as will be appreciated by those of ordinaryskill in the art.

In certain embodiments as otherwise described herein, the plaster wallpanel includes a first facing sheet covering an outer surface of thefirst plaster layer. The first facing sheet may be formed from a varietyof different materials, as will be appreciated by those of ordinaryskill in the art, including materials similar to the carrier facingdescribed above. For example, the facing sheet may be a paper facing ormay include a fiber mat. Further, the facing sheet may be embedded witha polymer or plaster material. In certain embodiments, the first facingsheet has an exposed outer surface. In other words, in some embodiments,the first facing sheet is the outermost layer of the wall panel and noadditional layers are disposed thereon. Such a plaster wall panel isshown in FIG. 5. Plaster wall panel 500 includes a first plaster layer530 and a second plaster layer 540 with a damping layer 550 disposedtherebetween. A first facing sheet 532 is disposed on first layer 530and has an exposed outer surface.

In certain embodiments as otherwise described herein, the first facingsheet contacts the first plaster material at the outer surface of thefirst plaster layer. In other words, in some embodiments, there are nolayers between the facing sheet and the first plaster material thatmakes up the first plaster layer. In other embodiments as otherwisedescribed herein, the plaster wall panel includes a thin layer of denseplaster disposed between and in contact with the first facing sheet andthe first plaster layer. In some embodiments, the thin layer of denseplaster has a thickness of less than 1.5 millimeters, e.g., a thicknessin a range of about 500 micrometers to about 1 millimeter, and a densitythat is greater than the first plaster material. Plaster wall panel 500,shown in FIG. 5, includes a thin layer of dense plaster 534 between thefirst facing sheet 532 and the first plaster layer 530.

In certain embodiments as otherwise described herein, the plaster wallpanel includes a second facing sheet covering an outer surface of thesecond plaster layer. As described above with respect to the firstfacing sheet, the second facing sheet may also be formed from a varietyof different materials. In certain embodiments, the second facing sheethas an exposed outer surface. In other words, in some embodiments, thesecond facing sheet is the outermost layer of the wall panel and noadditional layers are disposed thereon. For example, plaster wall panel500 includes a second facing sheet 542 disposed on second layer 540 andhas an exposed outer surface.

In certain embodiments as otherwise described herein, the second facingsheet contacts the second plaster material at the outer surface of thesecond plaster layer. In other embodiments as otherwise describedherein, the plaster wall panel includes a thin layer of dense plasterdisposed between and in contact with the second facing sheet and thesecond plaster layer. In some embodiments, the thin layer of denseplaster has a thickness of less than 1.5 millimeters, e.g., a thicknessin a range of about 500 micrometers to about 1 millimeter, and a densitythat is greater than the second plaster material. For example, plasterwall panel 500 includes a thin layer of dense plaster 544 between thesecond facing sheet 542 and the second plaster layer 540.

In some embodiments, the thin layer of dense plaster between the secondplaster layer and the second facing sheet has the same density as thefirst plaster layer. In such cases, in some embodiments, the thin layerof dense plaster is included between the second plaster layer and secondfacing sheet, but not between the first plaster layer and first facingsheet.

In certain embodiments as otherwise described herein, the plaster wallpanel has a damping loss factor that is at least 75% of the damping lossfactor of a symmetrical plaster wall panel of the same overall thicknesswhere both layers are formed of the second plaster material, e.g., atleast 80% of the damping loss factor of the symmetrical plaster wallpanel, e.g., at least 90% of the damping loss factor of the symmetricalplaster wall panel. For example, in some embodiments, the first materialis selected such that an asymmetrical position of the damping layerreduces the damping loss factor of the plaster wall panel by no morethan 25%, e.g., no more than 20%, e.g., no more than 10%. For example,in one embodiment, a plaster wall panel with a thickness of 16.2 mm hasthe damping layer offset from the center such that the thickness ratioof the first layer is 0.6, where the thickness ratio is defined as theratio of the thickness of the first layer to half the overall thicknessof the panel. In other words, in this embodiment, the first layer has athickness of −5 mm and the second layer has a thickness of −11 mm. Butthe elastic modulus of the first layer is nearly 1.5× that of the secondlayer, such that the damping loss factor is roughly equivalent to aplaster wall panel of 16.2 mm, where the layers are symmetrical and areboth formed of the second material. (This example is shown in FIG. 8 anddescribed in more detail below.)

Another aspect of the disclosure is a method for making a plaster wallpanel as described herein, the method including providing a first wetplaster precursor, providing a second wet plaster precursor, positioninga damping layer or a precursor therefor between the first wet plasterprecursor and the second wet plaster precursor. The method furtherincludes drying the first and second wet plaster precursors such thatthe first plaster precursor hardens into the first plaster layer havingthe first thickness and the second plaster precursor hardens into thesecond plaster layer having the second thickness. Such methods can bemade using processes familiar to the person of ordinary skill in theart, using standard procedures and equipment for making, e.g., gypsumwallboards.

FIG. 6 schematically depicts an apparatus for forming a plaster wallpanel according to a method of the disclosure. The process can, forexample, be completed using an in-line process. For example, in theembodiment of FIG. 6, a facing sheet of paper 642 is disposed on aplatform 660 (here, a conveyer travelling from right to left asindicated by the arrow). A second layer of wet plaster precursor 640 isdispensed on the facing sheet 642 (i.e., on the platform 660) viadispenser 662. The wet plaster precursor can be, e.g., a slurry ofgypsum, or another slurry, and can be of a viscosity that is typicallyused in the formation of plaster panels. A damping precursor layer 650is disposed on top of the second layer of wet plaster precursor 640, forexample, by being unrolled from a spool 664 (or multiple spoolsrespectively corresponding to multiple precursor sheets). The positionof rollers 666 and 668 may be adjustable to guide the damping precursorlayer 650 into a desired position (e.g., height) with respect to theplatform. The dispenser 670 is used to dispense the first layer of wetplaster precursor 630 on the damping precursor layer 650. Finally,another facing sheet of paper 632 is disposed on the first layer of wetplaster material 630. Thus, the wet plaster wall panel precursor 600includes the first and second layers of wet plaster precursor 630, 640,with the damping precursor layer 650 spread out between the wet plasterprecursor layers (i.e., between layers 640 and 630). The dispense ratiobetween the dispensers 662 and 670 can be used to control the thicknessof the layers of wet plaster precursor and, ultimately, the first andsecond plaster layers. This process can be run continuously, likeconventional gypsum wallboard manufacturing processes. The continuoussheet of plaster board can be divided as is conventional in the art,although extra care or processes may be necessary to cut the material ofthe damping layer.

The first and second wet plaster precursors are layers of wet plastermaterial that can be dried to provide first and second plaster layers asdescribed above. For each layer, the wet plaster material is a wet,formable, plaster material that can harden to provide the hardenedplaster material. The wet plaster material can be, for example, a gypsumslurry (i.e., when the hardened plaster material is a gypsum material).In other embodiments, the wet plaster material is a wet lime material ora wet cement material. But the person of ordinary skill in the art willappreciate that a variety of wet plaster materials can be used in thepractice of the processes as described herein. The wet plaster materialcan include any additives or fillers familiar to the person of ordinaryskill in the art, including those described above with respect to thehardened plaster material. The wet plaster material is desirably asemiliquid or otherwise formable mixture that can be, for example,dispensed and spread onto a surface such as a platform or conveyer.

In some embodiments, the damping precursor layer includes a carriersheet as described above with respect to the plaster wall panel. Thecarrier sheet may have a damping polymer or a damping polymer precursordisposed on its surface or embedded in the sheet. In other embodiments,the damping precursor layer is a sheet of a damping polymer, e.g.,without a carrier sheet. Such a material can be provided in roll form,or otherwise as will be appreciated by those of ordinary skill in theart. In certain embodiments, the polymer precursor material is amaterial that provides a viscoelastic polymer in the plaster wall panelsof the disclosure. In some embodiments, the polymer precursor is amaterial that cures during the hardening of the plaster (e.g., to form aviscoelastic polymer as described above). Accordingly, a carrier sheetcan be impregnated with a liquid or semiliquid thermally-curableformulation to be disposed between the wet plaster bodies. As theplaster of the layers hardens, the heat generated by the hardening caneffectively cure the formulation into the viscoelastic polymer.Alternatively, in some embodiments, the polymer precursor material is adamping polymer (e.g., as described above) disposed on a carrier sheet,that is disposed between the wet plaster precursor layers, with the wetplaster material hardening against it. In certain such cases, thedamping polymer is in a particulate or divided form, with the heatgenerated by the hardening of the plaster precursor layers beingsufficient to soften the damping polymer to allow it to intimatelycontact the plaster layers upon hardening. In certain embodiments, thedamping precursor sheet is prefabricated (e.g., in a separate process,or even offsite by a toll manufacturer).

In some embodiments, the damping polymer can be softened or even meltedby the heat generated during the hardening of the plaster, to form asubstantially continuous polymer material and to allow for intimatecontact with the hardened plaster material.

In some embodiments, instead of applying the damping layer or aprecursor thereof in sheet form (e.g., either as a carrier sheet withpolymer material or precursor disposed thereon, or as a sheet of polymermaterial) a precursor for the damping layer is applied to the surface ofthe second layer of wet plaster material in liquid or semisolid form,e.g., by spraying or otherwise dispensing a layer of a polymer precursorthereon. A first layer of wet plaster material is then disposed on thedamping layer. The polymer precursor can be cured before, after, orduring the application of the first layer of wet plaster material. Forexample, the polymer precursor can be cured at least in part with theheat generated by the drying of the wet plaster material.

EXAMPLES

Laminate plaster wall panels as described herein can be modeled usingprinciples of constrained layer damping, assuming a viscoelastic dampinglayer (having a thickness t, a density ρ, a shear modulus G* and adamping loss factor η) constrained between two layers of plaster (whichneed not be identical in properties, each having a thickness h, adensity ρ, a Young's modulus E, and a damping loss factor η). The designprinciples for such a structure is described by the RKU model, describedin D. Ross, E. E. Ungar and E. M. Kerwin, “Damping of plate flexuralvibrations by means of viscoelastic laminate” Structural Damping,Section II ASME, 1959, which is hereby incorporated herein by referencein its entirety. Using such principles, various simulations weregenerated for an Easi-Lite board formulation with a base formula havinga density of 540 kg/m³ and an approximate elastic modulus of 1.7 GPa.The simulations included an overall panel thickness of 15.8 mm, with arange of thicknesses used for the first plaster layer, or bottom layer,from 7.93 mm for the symmetrical default panel down to 1 mm for a veryasymmetrical panel. Material properties of the simulated boards werealso varied over a range of values. In particular, the elastic modulusof the first layer was varied from the default of 530 kg/m³ up to 1378kg/m³. Based on the varied elastic modulus, corresponding densities werecalculated using the density-elastic moduli relationship shown inequation (1):

$\begin{matrix}{\overset{˜}{E} = {\left( \frac{\overset{˜}{\rho}}{\rho_{s}} \right)^{2}E_{s}}} & (1)\end{matrix}$

where E_(S) and ρ_(S) denote the elastic modulus and density of unfoamedgypsum, respectively.

The damping loss factor for the various wall panels is shown in FIG. 7.The data shows that although the damping loss factor drops substantiallyas the wall panel becomes more asymmetrical, the reduction in thedamping loss factor can be substantially offset by varying the materialproperties of the first layer. In particular, FIG. 7 shows that anincrease in both elastic modulus and density of the thinner, first layeryields gains in damping loss factor over a wide range of layerthicknesses and density, when the panel is asymmetrical. On the otherhand, FIG. 7 also shows that asymmetry of the material properties canalso reduce the damping loss factor for a geometrically asymmetricalboard. Both of these findings support the conclusion that symmetry inthe flexural stiffness between the two layers enhances the damping lossfactor of the wall panel.

FIG. 8 illustrates the change in damping loss factor as a result ofchanges in thickness ratio and elastic modulus ratio, where thethickness ratio is defined as the thickness of the first layer over thehalf the thickness of the entire panel and the elastic modulus ratio isdefined as the modulus of the first layer over the modulus of the bottomlayer. FIG. 8 is based on simulations of a panel having a thickness of16.2 mm, with a damping layer that is 0.3 mm thick. The simulations showthe elastic modulus ratio between the first and second layers that isneeded for various thickness ratios in order to yield a damping lossfactor that is within 10% of the damping loss factor of a symmetricalboard.

FIG. 9 illustrates the average damping loss factor of three laminatestructures. All three sample structures were formed of two layersseparated by an interlayer of high damping BEH polymer (polyurethanefoam+acrylic adhesive). Each of the samples had an overall thickness of15.9 mm, a length of 600 mm, and a width of 25 mm. The first sample wassymmetrical and formed of two ¼ inch layers of white Delrin® AcetalResin Sheet, each having a bending stiffness of 1.5×10⁶ N/m. The secondsample was asymmetrical and formed of a ⅜ inch layer of Delrin® AcetalResin Sheet having a bending stiffness of 2.2×10⁶ N/m and a ⅛ inch layerDelrin® Acetal Resin Sheet having a bending stiffness of 7.5×10⁵ N/m.The third sample was also asymmetrical and formed of the ⅜ inch layer ofDelrin® Acetal Resin Sheet and a ⅛ inch layer of Multipurpose 6061aluminum sheet having a bending stiffness of 1.8×10⁷ N/m,

The three samples were secured as cantilever beams and were vibratedaccording to the first three vibration modes of a fixed-free beam. FIG.9 shows the average damping loss factor over all three vibration modesfor each of the samples. While the asymmetrical second sample thatincluded two layers of Acetal resin sheet had a substantially lowerdamping loss factor than the symmetrical first sample, the use of thestiffer aluminum layer in the third sample resulted in a higher dampingloss factor than the similarly shaped second sample. Results of thedamping loss factor for each individual vibration mode is shown in FIG.10.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the processes and devicesdescribed here without departing from the scope of the disclosure. Thus,it is intended that the present disclosure cover such modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

EMBODIMENTS

Embodiment 1. A plaster wall panel comprising:

-   -   a first plaster layer having a first thickness and being        composed of a first plaster material having a first material        property;    -   a second plaster layer having a second thickness and being        composed of a second plaster material having a second material        property, wherein the first thickness is smaller than the second        thickness and wherein the first and second material properties        are different; and    -   a damping layer disposed between the first plaster layer and the        second plaster layer.

Embodiment 2. The plaster wall panel according to embodiment 1, whereinat least one of the first plaster material and second plaster materialcomprises a base material that is a gypsum material.

Embodiment 3. The plaster wall panel according to embodiment 1 orembodiment 2, wherein at least one of the first plaster material andsecond plaster material comprises a base material that is lime or acement.

Embodiment 4. The plaster wall panel according to any of embodiments 1to 3, wherein the first thickness is in a range from 3% to 75% of thesecond thickness, e.g., from 5% to 50%, e.g., from 5% to 10%, or from10% to 20%, or from 20% to 30%, or from 30% to 40% or from 40% to 50%,e.g., 45% to 50%.

Embodiment 5. The plaster wall panel according to any of embodiments 1to 4, wherein the elastic modulus of the first plaster material isgreater than the elastic modulus of the second plaster material.

Embodiment 6. The plaster wall panel according to embodiment 5, whereinthe elastic modulus of the first plaster material is in a range from150% to 1000% of the elastic modulus of the second plaster material,e.g., from 150% to 200%, or from 200% to 300%, or from 300% to 400%, orfrom 400% to 500%, or from 500% to 600%, or from 600% to 700%, or from700% to 800%, or from 800% to 900% or from 900% to 1000%.

Embodiment 7. The plaster wall panel according to any of embodiments 1to 6, wherein the density of the first plaster material is greater thanthe density of the second plaster material.

Embodiment 8. The plaster wall panel according to embodiment 5, whereinthe density of the first plaster material is in a range from 110% to400% of the density of the second plaster material, e.g., from 120% to300%, e.g., from 120% to 150%, or from 150% to 200%, or from 200% to250%, or from 250% to 300%.

Embodiment 9. The plaster wall panel according to any of embodiments 1to 8, wherein the first material has a different composition than thesecond material.

Embodiment 10. The plaster wall panel according to embodiment 9, whereinthe first plaster material comprises a base material that is a gypsummaterial and the second plaster material comprises a base material thatis lime or a cement.

Embodiment 11. The plaster wall panel according to embodiment 9, whereinthe second plaster material comprises a base material that is a lime ora cement and the first plaster material comprises a base material thatis a gypsum material.

Embodiment 12. The plaster wall panel according to any of embodiments 1to 7, wherein the first plaster material and second plaster materialinclude a different concentrations of additives that impact the flexuralrigidity of the plaster layers, e.g., foaming agents, sodiumtrimetaphosphate, or polymer additives such as hydroxyethyl methylcellulose, polyvinyl acetate and dextrin.

Embodiment 13. The plaster wall panel according to any of embodiments 1to 12, wherein the first plaster layer includes a higher concentrationof reinforcing fibers than the second plaster layer.

Embodiment 14. The plaster wall panel according to any of embodiments 1to 10, wherein the first material and second materials are anisotropic,and wherein the orientation of the first material in the first plasterlayer is different than the orientation of the second material in thesecond plaster layer.

Embodiment 15. The plaster wall panel according to any of embodiments 1to 14, wherein the damping layer is formed of a damping polymer.

Embodiment 16. The plaster wall panel according to embodiment 15,wherein the damping polymer is a polyvinyl butyral.

Embodiment 17. The plaster wall panel according to embodiment 15,wherein the damping polymer is a silicone or an acrylic material.

Embodiment 18. The plaster wall panel according to any of embodiments 15to 17, wherein the damping polymer has a shear modulus in the range of10 kPa to 100 MPa.

Embodiment 19. The plaster wall panel according to any of embodiments 15to 18, wherein the damping polymer comprises or is filled with a fireresistant material and/or a mold resistant material.

Embodiment 20. The plaster wall panel according to any of embodiments 1to 19, wherein the damping loss factor for the damping layer is at least5%.

Embodiment 21. The plaster wall panel according to any of embodiments 1to 20, wherein the thickness of the plaster wall panel is at least 5 mm,e.g., in a range from 5 mm to 50 mm, e.g., in a range from 6 mm to 25mm, e.g., in a range from 6 mm to 20 mm, e.g., about 6 mm, or about 10mm, or about 13 mm, or about 16 mm.

Embodiment 22. The plaster wall panel according to any of embodiments 1to 21, wherein a length of the plaster wall panel is in a range from 6feet to 24 feet, e.g., in a range from 8 feet to 20 feet, e.g., about 8feet, about 9 feet, about 10 feet, about 12 feet, about 14 feet, about16 feet or about 20 feet.

Embodiment 23. The plaster wall panel according to any of embodiments 1to 22, wherein a width of the plaster wall panel is in a range from 24inches to 96 inches, e.g., from 36 inches to 72 inches, e.g., about 48inches or about 54 inches.

Embodiment 24. The plaster wall panel according to any of embodiments 1to 23, wherein a thickness of the damping layer is in a range of 0.05 mmto 4 mm, e.g., 0.2 mm to 2 mm, e.g., 0.3 mm to 1 mm.

Embodiment 25. The plaster wall panel according to any of embodiments 1to 24, wherein the damping layer extends continuously across an entirelength of the plaster wall panel.

Embodiment 26. The plaster wall panel according to any of embodiments 1to 24, wherein the damping layer extends continuously across a portionof the width of the plaster wall panel from within 5 inches of a firstlong edge of the plaster wall panel to within 5 inches of a second longedge of the plaster wall panel.

Embodiment 27. The plaster wall panel according to any of embodiments 1to 26, wherein the damping layer extends continuously across an entirewidth of the plaster wall panel.

Embodiment 28. The plaster wall panel according to any of embodiments 1to 26, wherein the damping layer extends continuously across a portionof the length of the plaster wall panel from within 5 inches of a firstshort edge of the plaster wall panel to within 5 inches of a secondshort edge of the plaster wall panel.

Embodiment 29. The plaster wall panel according to any of embodiments 1to 24, wherein the damping layer is segmented in a regular pattern,e.g., in strips or in a checkerboard pattern.

Embodiment 30. The plaster wall panel according to embodiment 29,wherein the regular pattern includes strips, and wherein the stripsextend continuously across one of the width or the length of the plasterwall panel.

Embodiment 31. The plaster wall panel according to any of embodiments 1to 30, wherein the damping layer has a first surface that contacts thefirst plaster layer and a second surface that contacts the secondplaster layer.

Embodiment 32. The plaster wall panel according to embodiment 31,wherein the damping layer includes a damping polymer that extends fromthe first surface to the second surface and contacts the first plasterlayer and the second plaster layer.

Embodiment 33. The plaster wall panel according to embodiment 31,wherein the damping layer includes a damping polymer disposed on acarrier sheet, e.g., of paper or fiber glass, and wherein the dampingpolymer contacts one of the first plaster layer or second plaster layer,and the carrier sheet contacts the other of the first plaster layer orsecond plaster layer.

Embodiment 34. The plaster wall panel according to any of embodiments 1to 32, further comprising a first facing sheet covering an outer surfaceof the first plaster layer, wherein the first facing sheet has anexposed outer surface.

Embodiment 35. The plaster wall panel according to embodiment 34,wherein the first facing sheet contacts the first plaster material atthe outer surface of the first plaster layer.

Embodiment 36. The plaster wall panel according to embodiment 34,further comprising a thin layer of dense plaster disposed between and incontact with the first facing sheet and the first plaster layer, whereinthe thin layer of dense plaster has a thickness of less than 1.5millimeters and a density that is greater than the first plastermaterial.

Embodiment 37. The plaster wall panel according to any of embodiments 1to 36, further comprising a second facing sheet covering an outersurface of the second layer, wherein the second facing sheet has anexposed outer surface.

Embodiment 38. The plaster wall panel according to embodiment 37,wherein the second facing sheet contacts the second plaster material atthe outer surface of the second plaster layer.

Embodiment 39. The plaster wall panel according to embodiment 37,further comprising a thin layer of dense plaster disposed between and incontact with the second facing sheet and the second plaster layer,wherein the thin layer of dense plaster has a thickness of less than 1.5millimeters and a density that is greater than the second plastermaterial.

Embodiment 40. The plaster wall panel according to any of embodiments 1to 39, wherein the plaster wall panel has a damping loss factor that isat least 75% of the damping loss factor of a symmetrical plaster wallpanel of the same overall thickness where both layers are formed of thesecond plaster material, e.g., at least 80% of the damping loss factorof the symmetrical plaster wall panel, e.g., at least 90% of the dampingloss factor of the symmetrical plaster wall panel.

Embodiment 41. A method of forming a plaster wall panel according to anyof embodiments 1 to 40, the method comprising:

-   -   providing a first wet plaster precursor;    -   providing a second wet plaster precursor;    -   positioning a damping layer or a precursor therefor between the        first wet plaster precursor and the second wet plaster        precursor; and    -   drying the first and second wet plaster precursors such that the        first plaster precursor hardens into the first plaster layer        having the first thickness and the second plaster precursor        hardens into the second plaster layer having the second        thickness.

Embodiment 42. The method according to embodiment 41, wherein providingthe second wet plaster precursor comprises dispensing the second wetplaster precursor onto a platform, such as a conveyor.

Embodiment 43. The method according to embodiment 41, where a facingsheet is disposed on the platform, such that the second wet plasterprecursor is disposed on the facing sheet.

Embodiment 44. The method according to any of embodiments 41 to 43,wherein positioning the damping layer or precursor therefor between thefirst wet plaster precursor and the second wet plaster precursorincludes unrolling the damping layer or precursor therefor onto thesecond wet plaster precursor.

Embodiment 45. The method according to any of embodiments 41 to 44,wherein hardening of at least one of the first and second wet plasterprecursor generates sufficient heat to soften a polymer precursor forthe damping layer.

Embodiment 46. The method according to any of embodiments 41 to 45,wherein hardening of at least one of the first and second wet plasterprecursor generates sufficient heat to cure a polymer precursor for thedamping layer.

What is claimed is:
 1. A plaster wall panel comprising: a first plasterlayer having a first thickness and being composed of a first plastermaterial having a first material property; a second plaster layer havinga second thickness and being composed of a second plaster materialhaving a second material property, wherein the first thickness issmaller than the second thickness and wherein the first and secondmaterial properties are different; and a damping layer disposed betweenthe first plaster layer and the second plaster layer.
 2. The plasterwall panel according to claim 1, wherein at least one of the firstplaster material and second plaster material comprises a base materialthat is a gypsum material.
 3. The plaster wall panel according to claim1, wherein at least one of the first plaster material and second plastermaterial comprises a base material that is lime or a cement.
 4. Theplaster wall panel according to claim 1, wherein the first thickness isin a range from 3% to 75% of the second thickness.
 5. The plaster wallpanel according to claim 1, wherein the elastic modulus of the firstplaster material is in a range from 150% to 1000% of the elastic modulusof the second plaster material.
 6. The plaster wall panel according toclaim 1, wherein the density of the first plaster material is in a rangefrom 110% to 400% of the density of the second plaster material.
 7. Theplaster wall panel according to claim 1, wherein the first material hasa different composition than the second material.
 8. The plaster wallpanel according to claim 7, wherein the first plaster material andsecond plaster material include different concentrations of additivesthat impact the flexural rigidity of the plaster layers.
 9. The plasterwall panel according to claim 1, wherein the damping layer is formed ofa damping polymer.
 10. The plaster wall panel according to claim 9,wherein the damping polymer has a shear modulus in the range of 10 kPato 100 MPa.
 11. The plaster wall panel according to claim 9, wherein thedamping polymer comprises or is filled with a fire resistant materialand/or a mold resistant material.
 12. The plaster wall panel accordingto claim 1, wherein the damping layer has a first surface that contactsthe first plaster layer and a second surface that contacts the secondplaster layer.
 13. The plaster wall panel according to claim 12, whereinthe damping layer includes a damping polymer that extends from the firstsurface to the second surface and contacts the first plaster layer andthe second plaster layer.
 14. The plaster wall panel according to claim1, wherein the damping layer includes a damping polymer disposed on acarrier sheet, e.g., of paper or fiber glass, and wherein the dampingpolymer contacts one of the first plaster layer or second plaster layer,and the carrier sheet contacts the other of the first plaster layer orsecond plaster layer.
 15. The plaster wall panel according to claim 1,wherein the plaster wall panel has a damping loss factor that is atleast 75% of the damping loss factor of a symmetrical plaster wall panelof the same overall thickness where both layers are formed of the secondplaster material.
 16. A method of forming a plaster wall panel, themethod comprising: providing a first wet plaster precursor; providing asecond wet plaster precursor; positioning a damping layer or a precursortherefor between the first wet plaster precursor and the second wetplaster precursor; and drying the first and second wet plasterprecursors such that the first plaster precursor hardens into a firstplaster layer having a first thickness and being composed of a firstplaster material having a first material property and the second plasterprecursor hardens into a second plaster layer having a second thicknessand being composed of a second plaster material having a second materialproperty, wherein the first and second material properties aredifferent.
 17. The method according to claim 16, wherein providing thesecond wet plaster precursor comprises dispensing the second wet plasterprecursor onto a platform, such as a conveyor.
 18. The method accordingto claim 16, wherein positioning the damping layer or precursor thereforbetween the first wet plaster precursor and the second wet plasterprecursor includes unrolling the damping layer or precursor thereforonto the second wet plaster precursor.
 19. The method according to claim16, wherein hardening of at least one of the first and second wetplaster precursor generates sufficient heat to soften a polymerprecursor for the damping layer.
 20. The method according to claim 16,wherein hardening of at least one of the first and second wet plasterprecursor generates sufficient heat to cure a polymer precursor for thedamping layer.